OBJECTIVE: To describe patterns of association between different groups of young orphans and vulnerable children (OVC) and their nutritional and health outcomes; and to develop a theoretical framework to analyse the determinants of child malnutrition and ill-health, and identify the different mechanisms which contribute to these outcomes in such children. METHODS: We developed and tested a theoretical framework to explain why orphans and vulnerable children experience more ill-health and malnutrition based on statistical analysis of data on 31 672 children aged 0-17 years (6753 aged under 5 years) selected from the Zimbabwe OVC Baseline Survey 2004. RESULTS: 28% of children aged 0-4 years at last birthday were either orphans or vulnerable children. They were more likely than non-vulnerable children to have suffered recently from diarrhoeal illness (age- and sex-adjusted odds ratio, AOR, 1.27; 95% CI 1.09-1.48) and acute respiratory infection (1.27; 1.01-1.59) and to be stunted (1.24; 1.09-1.41) and underweight (1.18; 1.02-1.36). After further adjustment for exposure to extreme poverty, OVC remained at greater risk of diarrhoeal disease (AOR 1.25; 1.07-1.46) and chronic malnutrition (1.21; 1.07-1.38). In 0-17-year-olds, OVC with acute respiratory infection were more likely not to have received any treatment even after adjusting for poverty (AOR 1.29; 95% CI 1.16-1.43). CONCLUSION: Differences in exposure to extreme poverty among young children by OVC status were relatively small and did not explain the greater malnutrition and ill-health seen in OVC.